Analysis of Three-dimensional Atom-probe Data by the Proximity Histogram

Abstract

The three-dimensional (3D) atom-probe technique produces a reconstruction of the elemental chemical identities and three-dimensional positions of atoms field evaporated from a sharply pointed metal specimen, with a local radius of curvature of less than 50 nm. The number of atoms collected can be on the order of one million, representing an analysis volume of approximately 20 nm × 20 nm × 200 nm (80,000 nm3). This large amount of data allows for the identification of microstructural features in a sample, such as grain or heterophase boundaries, if the feature density is large enough. Correlation of the measured atomic positions with these identified features results in an atom-by-atom description of the chemical environment of crystallographic defects. This article outlines a data compilation technique for the generation of composition profiles in the vicinity of interfaces in a geometrically independent way. This approach is applied to quantitative determination of interfacial segregation of silver at a MgO/Cu(Ag) heterophase interface.

Nanoscale Characterization of Elemental Partitioning between Gamma and Gamma Prime Phases in René 88 DT Nickel-Base Superalloy

“…The compositional profile across the c¢/c interfaces for the WQ0 sample has been determined using a powerful analysis tool, the proximity histogram (proxigram in short) [11] for the various c¢ precipitates, visible in the reconstructions shown in Figures 2(c) and (d). These proxigrams can be used for any internal surface, even those involving a complex topology.…”

“…While these values of compositional widths can be used as qualitative guidelines, it is important to realize that the x-axis in the proxigrams shown in Figures 3(a), 6(a), and 9 does not strictly correspond to a linear distance scale, but more appropriately to proximity to the interface. [11] Thus, while this distance is more representative of a linear distance in case of planar c/c¢ interfaces, the situation can change as the interface becomes more curved and complex in shape. Nevertheless, comparing the three proxigrams, it is rather interesting that the compositional gradient appears to decrease with increasing aging time in these samples with the sharpest gradient appearing in case of the WQ0 sample.…”

Prototype evaluation of transformation toughened blast resistant naval hull steels: Part II

“…The negative values in abscissa represent the matrix composition while the positive values are indicative of the precipitate compositions. However, the zero point is not necessarily a correct estimate of the precipitate/matrix interface and serves as an approximate reference point (9). The proxigram obtained from analysis of copper precipitates in the single-step temper sample is presented in Fig.…”

“…The average matrix and precipitate compositions and the concentration of the various solute atoms near the matrix/precipitate interface can be investigated by a proximity histogram, or "proxigram", available in ADAM, developed and implemented by Hellman et al (9). The concentration values were determined by averaging the concentration in 0.2 nm peripheral shells around all the precipitates with respect to the 10at% copper isoconcentration surface, within and outside the precipitates.…”

“…Systematic errors that may interfere with the collection of specific elements such as carbon may be an additional source of error. The data from 3DAP were analyzed and visualized by the software ADAM developed by Hellman et al (7), providing a range of tools to analyze 3DAP data (8,9), including the ability to define planar or cylindrical regions of interest and perform analyses such as concentration profiles, ladder diagrams and composition maps with respect to a region of interest. Isoconcentration surfaces were employed to examine the size and shape of precipitates.…”